1. Technical Field of the Invention
The present invention relates to a compressor and an electric motor for same.
2. Description of Related Art
Compressor includes a compression mechanism and an electric motor for driving same accommodated within a housing. Normally, the stator of the electric motor is fixed to the housing of the compressor by means of shrinkage-fitting, fitting and welding, bolting, or the like, so as to operate efficiently and stably with a certain air gap between itself and the rotor.
Conventional compressor employs thick slot insulating paper or provides a small slot space to prevent current leakage from the electric motor to the housing, thereby compensating the operation efficiency of the electric motor.
Another problem encountered by conventional compressors was the vibration of the electric motor which is directly transmitted to the housing of the compressor and leads to adverse effects on surrounding equipment and which also causes noise. The stator of the electric motor is normally iron-based, whereas the housing to which the stator is fitted is made of non-ferrous metal having a greater coefficient of thermal expansion than iron. Therefore, as the temperature rises with the operation of the electric motor, a gap develops between the housing and the stator due to the difference in thermal expansion thereof. This may cause undesirable backlash and vibration. The difference in thermal expansion coefficient also leads to metal fatigue and decrease in strength of the housing because of the stress caused by repeated expansion and contraction concomitant with activation and deactivation of the electric motor.
An object of the present invention is to prevent the leakage of current from an electric motor to a compressor housing or a motor casing without deteriorating the operation efficiency of the electric motor.
Another object of the present invention is to prevent backlash, vibration, and decrease in strength in compressors due to temperature rise occurring with the operation of the electric motor.
To achieve the above-described objects, the present invention provides an electric motor accommodated fixedly in position within its own casing or a housing of a compressor, having a non-conductive member between its stator and the casing or the housing, for preventing the stator and the casing or housing from making contact with each other. The non-conductive member is made of a material having a thermal expansion coefficient greater than that of the stator, such as resin.
The housing or the casing is made of a non-ferrous metal material, such as aluminum or magnesium.
The non-conductive member is most preferably made of a resin because of its light weight and high insulation property.
The non-conductive member may also be made of a water glass, because it is stable against heat and is thus useful in shrinkage-fitting the stator to the housing or the casing.
Further, the non-conductive material may be made from an inorganic substance having a thermal expansion coefficient intermediate between the thermal expansion coefficient of the stator and that of the compressor housing or the motor casing by means of vapor-deposition or powder coating. The non-conductive material thus realized is also stable against heat and is thus useful in shrinkage-fitting the stator to the compressor housing or the motor casing.